a baby chick with a swollen bottom

Not sure what it is called (vent?) 1 week old is pink and swollen she had a pasty buy yesterday I washed it removed dry junk and put some vasoline it looks clean but pink and swollen. Any Ideas I am a newbe

You might want to dust a little Aeromycin powder on her hiney (some will absorb through skin, especially if she's raw there) or add some to water for a few days to help her out in case she's got any infection causing the swelling.
Best wishes.